VSB communication system

ABSTRACT

A VSB communication system comprises a VSB transmission system and a VSB reception system. The VSB transmission system multiplexes a coded MPEG data and a coded supplemental data having a null sequence inserted therein, with required multiplexing information included in a field synchronization signal or in a supplemental data according to a number of the supplemental data packets being transmitted. The VSB reception system detects the required multiplexing information from the field synchronization signal or the supplemental data and decodes the multiplexed data by using the null sequence and the detected multiplexing information, as well as demultiplexes the multiplexed data into the MPEG data and the supplemental data.

CROSS REFERENCE TO RELATED ART

This application claims the benefit of Korean Patent Application Nos.2001-20929 and 2001-28405, filed on Apr. 18, 2001 and May 23, 2001,respectively, which are hereby incorporated by reference in theirentirety.

This application incorporates by reference in their entirety co-pendingU.S. application serial number ______, mailed via Express Mail No.EF334462226US entitled “VSB TRANSMISSION SYSTEM FOR PROCESSINGSUPPLEMENTAL TRANSMISSION DATA” and serial number ______, mailed viaExpress Mail No. ET235110894US entitled “VSB RECEPTION SYSTEM WITHENHANCED SIGNAL DETECTION FOR PROCESSING SUPPLEMENTAL DATA.”

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a digital television transmissionsystem, and more particularly, to a 8T-VSB (Vestigial Sideband)communication system for transmitting and receiving supplemental data inaddition to MPEG data and to a signal format for the VSB communicationsystem.

2. Description of the Related Art

The United States of America has employed ATSC 8T-VSB (8Trellis-Vestigial Sideband) as a standard since 1995, and has beenbroadcasting in the ATSC 8T-VSB since the later half of 1998. SouthKorea also has employed the ATSC 8T-VSB as a standard. South Koreastarted test broadcasting in May 1995, and has since August 2000 put inplace a regular test broadcasting system. The advancement of technologyallows the transmission of digital television (DTV) in the same 6 MHzbandwidth currently used by NTSC.

FIG. 1B illustrates a block diagram of a conventional ATSC 8T-VSBtransmission system 6 (“VSB transmission system”). The VSB transmissionsystem 6 generally comprises a data randomizer 11, Reed-Solomon coder12, data interleaver 13, Trellis coder 14, multiplexer 15, pilotinserter 16, VSB modulator 17 and RF converter 18.

Referring to FIG. 1B, there is a data randomizer 11 for receiving andmaking random MPEG data (video, audio and ancillary data). The datarandomizer 11 receives the MPEG-II data output from an MPEG-II encoder.Although not shown in FIG. 1B, the MPEG-II encoder takes basebanddigital video and performs bit rate compression using the techniques ofdiscrete cosine transform, run length coding, and bi-directional motionprediction. The MPEG-II encoder then multiplexes this compressed datatogether with pre-coded audio and any ancillary data that will betransmitted. The result is a stream of compressed MPEG-II data packetswith a data frequency of only 19.39 Mbit/Sec. The MPEG-II encoderoutputs such data to the data randomizer in serial form. MPEG-II packetsare 188 bytes in length with the first byte in each packet always beingthe sync or header byte. The MPEG-II sync byte is then discarded. Thesync byte will ultimately be replaced by the ATSC segment sync in alater stage of processing.

In the VSB transmission system 6, the 8-VSB bit stream should have arandom, noise-like signal. The reason being that the transmitted signalfrequency response must have a flat noise-like spectrum in order to usethe allotted 6 MHz channel space with maximum efficiency. Random dataminimizes interference into analog NTSC. In the data randomizer 11, eachbyte value is changed according to known pattern of pseudo-random numbergeneration. This process is reversed in the VSB receiver in order torecover the proper data values.

The Reed-Solomon coder 12 of the VSB transmission system 6 is used forsubjecting the output data of the data randomizer 11 to Reed-Solomoncoding and adding a 20 byte parity code to the output data. Reed Solomonencoding is a type of forward error correction scheme applied to theincoming data stream. Forward error correction is used to correct biterrors that occur during transmission due to signal fades, noise, etc.Various types of techniques may be used as the forward error correctionprocess.

The Reed-Solomon coder 12 takes all 187 bytes of an incoming MPEG-IIdata packet (the sync or header byte has been removed from 188 bytes)and mathematically manipulates them as a block to create a digitalsketch of the block contents. This “sketch” occupies 20 additional byteswhich are added at the tail end of the original 187 byte packet. These20 bytes are known as Reed-Solomon parity bytes. The 20 Reed-Solomonparity bytes for every data packet add redundancy for forward errorcorrection of up to 10 byte errors/packet. Since Reed-Solomon decoderscorrect byte errors, and bytes can have anywhere from 1 to 8 bit errorswithin them, a significant amount of error correction can beaccomplished in the VSB reception system. The output of the Reed-Solomoncoder 12 is 207 bytes (187 plus 20 parity bytes).

The VSB reception system will compare the received 187 byte block to the20 parity bytes in order to determine the validity of the recovereddata. If errors are detected, the receiver can use the parity bytes tolocate the exact location of the errors, modify the corrupted bytes, andreconstruct the original information.

The data interleaver 13 interleaves the output data of the Reed-Solomoncoder 12. In particular, the data interleaver 13 mixes the sequentialorder of the data packet and disperses or delays the MPEG-II packetthroughout time. The data interleaver 13 then reassembles new datapackets incorporating small sections from many different MPEG-II(pre-interleaved) packets. The reassembled packets are 207 bytes each.

The purpose of the data interleaver 13 is to prevent losing of one ormore packets due to noise or other harmful transmission environment. Byinterleaving data into many different packets, even if one packet iscompletely lost, the original packet may be substantially recovered frominformation contained in other packets.

The VSB transmission system 6 also has a trellis coder 14 for convertingthe output data of the data interleaver 13 from byte form into symbolform and for subjecting it to trellis coding. In the trellis coder 14,bytes from the data interleaver 13 are converted into symbols andprovided one by one to a plurality of Trellis coders and precoders shownin FIG. 9.

Trellis coding is another form of forward error correction. UnlikeReed-Solomon coding, which treated the entire MPEG-II packetsimultaneously as a block, trellis coding is an evolving code thattracks the progressing stream of bits as it develops through time.

The trellis coder 14 adds additional redundancy to the signal in theform of more (than four data levels, creating the multilevel (8) datasymbols for transmission. For trellis coding, each 8-bit byte is splitup into a stream of four, 2-bit words. In the trellis coder 14, each2-bit input word is compared to the past history of previous 2-bitwords. A 3-bit binary code is mathematically generated to describe thetransition from the previous 2-bit word to the current one. These 3-bitcodes are substituted for the original 2-bit words and transmitted asthe eight level symbols of 8-VSB. For every two bits that enter thetrellis coder 14, three bits are produced.

The trellis decoder in the VSB receiver uses the received 3-bittransition codes to reconstruct the evolution of the data stream fromone 2-bit word to the next. In this way, the trellis coder follows a“trail” as the signal moves from one word to the next through time. Thepower of trellis coding lies in its ability to track a signal's historythrough time and discard potentially faulty information (errors) basedon a signal's past and future behavior.

A multiplexer 15 is used for multiplexing a symbol stream from thetrellis coder 14 and synchronizing signals. The segment and the fieldsynchronizing signals provide information to the VSB receiver toaccurately locate and demodulate the transmitted RF signal. The segmentand the field synchronizing signals are inserted after the randomizationand error coding stages so as not to destroy the fixed time andamplitude relationships that these signals must possess to be effective.The multiplexer 15 provides the output from the trellis coder 14 and thesegment and the field synchronizing signals in a time division manner.

An output packet of the data interleaver 13 comprises the 207 bytes ofan interleaved data packet. After trellis coding, the 207 byte segmentis stretched out into a baseband stream of 828 eight level symbols. Thesegment synchronizing signal is a four symbol pulse that is added to thefront of each data segment and replaces the missing first byte (packetsync byte) of the original MPEG-II data packet. The segmentsynchronizing signal appears once every 832 symbols and always takes theform of a positive-negative-positive pulse swinging between the +5 and−5 signal levels.

The field synchronizing signal is an entire data segment that isrepeated once per field. The field synchronizing signal has a known datasymbol pattern of positive-negative pulses and is used by the receiverto eliminate signal ghosts caused by poor reception.

The VSB transmission system 6 also has the pilot inserter 16 forinserting pilot signals into the symbol stream from the multiplexer 15.Similar to the synchronizing signals described above, the pilot signalis inserted after the randomization and error coding stages so as not todestroy the fixed time and amplitude relationships that these signalsmust possess to be effective.

Before the data is modulated, a small DC shift is applied to the 8T-VSBbaseband signal. This causes a small residual carrier to appear at thezero frequency point of the resulting modulated spectrum. This is thepilot signal provided by the pilot inserter 16. This gives the RF PLLcircuits in the VSB receiver something to lock onto that is independentof the data being transmitted.

After the pilot signal has been inserted by the pilot inserter 16, theoutput is subjected to a VSB modulator 17. The VSB modulator 17modulates the symbol stream from the pilot inserter 16 into an 8 VSBsignal of an intermediate frequency band. The VSB modulator 17 providesa filtered (root-raised cosine) IF signal at a standard frequency (44Mhz in the U.S.), with most of one sideband removed.

In particular, the eight level baseband signal is amplitude modulatedonto an intermediate frequency (IF) carrier. The modulation produces adouble sideband IF spectrum about the carrier frequency. The totalspectrum is too wide to be transmitted in the assigned 6 MHz channel.

The sidelobes produced by the modulation are simply scaled copies of thecenter spectrum, and the entire lower sideband is a mirror image of theupper sideband. Therefore using a filter, the VSB modulator discards theentire lower sideband and all of the sidelobes in the upper sideband.The remaining signal (upper half of the center spectrum) is furthereliminated in one-half by using the Nyquist filter. The Nyquist filteris based on the Nyquist Theory, which summarizes that only a ½ frequencybandwidth is required to transmit a digital signal at a given samplingrate.

Finally, there is an RF (Radio Frequency) converter 18 for convertingthe signal of an intermediate frequency band from the VSB modulator 17into a signal of a RF band signal, and for transmitting the signal to areception system through an antenna 19.

The foregoing VSB communication system is at least partially describedin U.S. Pat. Nos. 5,636,251, 5,629,958 and 5600677 by Zenith Co. whichare incorporated herein by reference. The 8T-VSB transmission system,which is employed as the standard digital TV broadcasting in NorthAmerica and South Korea, was developed for the transmission of MPEGvideo and audio data. As technologies for processing digital signalsdevelop and the use of the Internet increases, the trend currently is tointegrate digitized home appliances, the personal computer, and theInternet into one comprehensive system.

Therefore, in order to satisfy the variety of the demands of users,there is a need to develop a communication system that facilitates theaddition and transmittal of a variety of supplemental data to the videoand audio data through the digital broadcasting channel. It is predictedthat the use of supplemental data broadcasting may require PC (PersonalComputer) cards or portable appliances, with simple indoor antennas.

However, there can be a substantial reduction of signal strength due towalls and nearby moving bodies. There also can be ghost and noise causedby reflective waves, which causes the performance of the signal of thesupplemental data broadcasting to be substantially poor. Supplementaldata broadcasting is different from general video and audio data in thatit requires a lower error ratio in transmission. For general video andaudio data, errors imperceptible to the human eye or ear areinconsequential. In contrast, for supplemental data, even one bit oferror in the supplemental data (which may include program executionfiles, stock information, and other similar information) may cause aserious problem. Therefore, the development of a communication systemthat is more resistant to the ghost and noise occurring on the channelis absolutely required.

In general, the supplemental data is transmitted by a time divisionsystem on a channel similar to the MPEG video and audio data. After theincorporation of digital broadcasting, there has already been awidespread emergence in the home appliance market of receivers equippedto receive ATSC VSB digital broadcast signals. These products receiveMPEG video and audio data only. Therefore, it is required that thetransmission of supplemental data on the same channel as the MPEG videoand audio data has no adverse influence on the existing receivers thatare equipped to receive ATSC VSB digital broadcasting. Such objective isdefined as ATSC VSB backward compatibility, and the supplemental databroadcasting system must be a system that is backward-compatible withthe ATSC VSB communication system.

In the meantime, in a poor channel environment, the receptionperformance of the existing ATSC VSB reception system may decrease.Because the supplemental data and the MPEG data are multiplexed insegment units, the order of multiplexing is closely related to thereceiving performance of the supplemental data. That is, the receivingperformance of the supplemental data may be significantly poor dependingon the order of multiplexing.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a VSB communicationsystem that substantially obviates one or more of the problems due tolimitations and disadvantages of the related art.

An object of the present invention is to provide a new VSB communicationsystem which is suitable for transmission of a supplemental data, androbust to noise and ghost (multipath).

Another object of the present invention is to provide a VSBcommunication system that can enhance receiving performance.

A further object of the present invention is to provide a method formultiplexing supplemental data and MPEG data in a VSB communicationsystem, and for improving receiving performance of the VSB communicationsystem.

Additional features and advantages of the invention will be set forth inthe description that follows, and in part will be apparent from thedescription, or may be learned by the practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, segments ofsupplemental data packets received through a first path of a VSBcommunication system and segments of MPEG transport packets receivedthrough a second path of the VSB communication system are multiplexedunder a fixed rule within a data field.

According to an embodiment of the present invention, a VSB communicationsystem comprises a VSB transmission system for multiplexing a coded MPEGdata and a coded supplemental data having a null sequence insertedtherein with required multiplexing information included theretoaccording to supplemental data packets, and transmitting a multiplexeddata field; and a VSB reception system for detecting the requiredmultiplexing information from the multiplexed data field, decoding themultiplexed data field by using the null sequence and the detectedmultiplexing information, and demultiplexing the multiplexed data intothe MPEG data and the supplemental data in response to the multiplexinginformation. Preferably, the multiplexing information of thesupplemental data is within the multiplexed data field. The preferredmultiplexing ratio of the supplemental data and the MPEG data is onesegment to one segment (1:1) or one segment to three segments (1:3).

According to an aspect of the present invention, the number of thesupplemental data packets multiplexed within one multiplexed data fieldis preferably between 0 to 156. The multiplexing information iscontained in at least one of a reserved area of a field synchronizingsignal segment in the multiplexed data field and a first supplementaldata segment after the field synchronizing signal segment.

According to another aspect of the present invention, the multiplexinginformation is in the reserved area that includes 92 symbols having afirst value (preferably a current ‘P’ value, a second value (preferablya count down value before changing the current ‘P’ value) and a thirdvalue (preferably a next ‘P’ value to be changed). The current ‘P’ valueoccupies at least 8 bits, count down value occuplies at least 8 bits,and the next ‘P’ value to be changed occupies at least 8 bits.Preferably, the reserved area is divided into first and second 12 bitsections, the first and the second 12 bit section being inverted withrespect to each other. The second 12 bit section is a bit-wise inversionof the first 12 bit section.

A method for processing MPEG and supplemental data packets in a VSBtransmission system with a supplemental data coder is described. In suchprocess, the supplement data coder generates coded supplemental datapackets from the supplemental data packets. The method comprises thesteps of multiplexing the coded supplemental data packets and MPEG datapackets in at least one data field, the data field having a plurality ofsegments, each segment corresponding to at least one of the codedsupplemental data packets and the MPEG data packets, wherein themultiplexing is performed in response to a number of the supplementaldata packets; and modulating the multiplexed data field in the VSBtransmission system.

The method further comprises subjecting the supplemental data packets toReed-Solomon coding for error correction; inserting a null sequence intothe Reed-Solomon coded supplemental data packets; and adding the MPEGheader to the supplemental data packets having the null sequenceinserted therein to obtain the coded supplemental data packets. Thesupplemental data packets may be subjected to interleaving for enhancingresistance to burst noise.

A method for processing MPEG and coded supplemental data packets in aVSB reception system having a supplemental data decoder to generate thesupplemental data packets from the coded supplemental data packets isdescribed. The method comprises the steps of detecting multiplexinginformation from a data field received by the VSB reception system, themultiplexing information being prepared in response to a number of thesupplemental data packets and containing demultiplexing information forseparating supplemental data segments and the MPEG data segments;demultiplexing the data field into the MPEG data packets and the codedsupplemental data packet by using the multiplexing information; andusing the supplemental data decoder, decoding the coded supplementaldata packets to obtain the supplemental data packets.

Alternatively, a method for multiplexing MPEG data and supplemental datain a VSB transmission system comprises the steps of determining a numberof supplemental data packets to be multiplexed with MPEG data segmentsin a data field, wherein the data field includes a plurality of MPEG andsupplemental data segements; and assigning a position of thesupplemental data segment to every Y segment of the data field startingfrom a preselected start position of the data field in sequential orderuntil the end of the data field, and assigning remaining supplementaldata segments to every Y segment of the data field starting from asubsequent start position that is offset by a predefined offset positionfrom a previous start position of the data field.

According to an aspect of the present invention, Y is preferably everyfourth segment and the predefined offset position is one segment. Inaddition, the preselected start position is preferably adjacent to afield synchronization signal segment.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

FIG. 1A illustrates a block diagram showing a VSB transmission systemand a supplemental data encoder in a VSB communication system inaccordance with a preferred embodiment of the present invention;

FIG. 1B illustrates a block diagram of a VSB transmission system in FIG.1A;

FIG. 2 illustrates a data field diagram in a case where the VSB signalcommunication system of the present invention has a poor decodingperformance;

FIG. 3 illustrates a data field diagram in a case where supplementaldata and MPEG data are multiplexed in a 1:3 ratio in a VSB signalcommunication system of the present invention;

FIG. 4 illustrates a data field diagram in a case where supplementaldata and MPEG data are multiplexed in a 1:1 ratio in a VSB signalcommunication system of the present invention;

FIG. 5A illustrates a multiplexed data field diagram when thesupplemental data segments and the MPEG data segments are multiplexed ina 1:3 ratio with the offset K1 set to ‘0’;

FIG. 5B illustrates a multiplexed data field diagram when thesupplemental data segments and the MPEG data segments are multiplexed ina 1:3 ratio with the offset K1 set to ‘1’;

FIG. 5C illustrates a multiplexed data field diagram when thesupplemental data segments and the MPEG data segments are multiplexed ina 1:3 ratio with the offset K1 set to ‘2’;

FIG. 5D illustrates a multiplexed data field diagram when thesupplemental data segments and the MPEG data segments are multiplexed ina 1:3 ratio with the offset K1 set to ‘3’;

FIG. 6A illustrates a multiplexed data field diagram when thesupplemental data segments and the MPEG data segments are multiplexed ina 1:1 ratio with the offset K1 set to ‘0’ and the offset K2 set to 1;

FIG. 6B illustrates a multiplexed data field diagram when thesupplemental data segments and the MPEG data segments are multiplexed ina 1:1 ratio with the offset K1 set to ‘0’ and the offset K2 set to 2;

FIG. 7 illustrates a functional diagram of a data interleaver of the VSBtransmission system;

FIG. 8 illustrates a diagram showing data input/output of the datainterleaver;

FIG. 9 illustrates a functional diagram showing a Trellis coder of theVSB transmission system;

FIG. 10 illustrates a segment structure of a field synchronizing signalsegment of a data field according to the preferred embodiment of thepresent invention;

FIG. 11 illustrates a block diagram showing a VSB reception system in aVSB signal communication system of the present invention; and

FIG. 12 illustrates a block diagram of the multiplexing informationdetector.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

The VSB communication system according to a preferred embodiment of thepresent invention includes a transmission system and a reception system.In FIG. 1A, the VSB transmitter 110 in accordance with a preferredembodiment of the present invention includes a VSB supplemental dataencoder 8 and a VSB transmission system 6. The description of the VSBtransmission system 6 is described above in connection with FIG. 1B, andthus, will not be repeated. According to the preferred embodiment of thepresent invention, the VSB supplemental data encoder 8 includes aReed-Solomon coder 1, a data interleaver 2, a null sequence inserter 3,an MPEG header inserter 4, a multiplexer 5, an 8T-VSB transmissionsystem 6, and an antenna 7.

As shown in FIG. 1A, for the transmission of the supplemental data fromthe VSB transmitter 110 (i.e., a broadcasting station) to a VSBreception system on a channel (terrestrial or cable), the VSBtransmitter 110 subjects the supplemental data to various digital signalprocesses. To provide backward compatibility of the present inventionwith existing devices, the supplemental data is preferably 164 bytepacket which will eventually be processed to be a 187 byte packet beforeentering the VSB transmission system 16. However, the size of thesupplemental data packet may be varied so long as the output of the VSBsupplemental data encoder 8 is compatible with the VSB transmissionsystem 6.

In the VSB supplemental data encoder 8, there is provided a Reed-Solomoncoder 1 for the correction of errors. The supplemental data is coded ata Reed-Solomon coder (or R-S coder) 1. Preferably, the Reed-Solomoncoder 1 is used for subjecting the supplemental data to Reed-Solomoncoding and adding a 20 byte parity code to the output data. As describedabove, Reed Solomon encoding is a type of forward error correctionscheme applied to the incoming data stream. Forward error correction isused to correct bit errors that occur during transmission due to signalfades, noise, etc. Various other types of error correction techniquesknown to one of ordinary skill in the art may be used as the forwarderror correction process.

According to the preferred embodiment, the Reed-Solomon coder 1 of theVSB supplemental data encoder 8 takes 164 bytes of an incomingsupplemental data packet and mathematically manipulates them as a blockto create a digital sketch of the block contents. The 20 additionalbytes are added at the tail end of the original 164 byte packet. These20 bytes are known as Reed-Solomon parity bytes. Since Reed-Solomondecoders of the VSB reception system correct byte errors, and bytes canhave anywhere from 1 to 8 bit errors within them, a significant amountof error correction can be accomplished in the VSB receiver. The outputof the Reed-Solomon coder 1 is preferably 184 bytes (164 bytes from theoriginal packet plus 20 parity bytes).

The VSB supplemental data encoder 8 further includes the datainterleaver 2, which interleaves the output data of the Reed-Solomoncoder 1. The data interleaver 2 is for interleaving the codedsupplemental data to enhance performance against burst noise. The datainterleaver 2 may be omitted without deviating from the gist of thepresent invention.

The data interleaver 2 according to the preferred embodiment mixes thesequential order of the supplemental data packet and disperses or delaysthe supplemental data packet throughout time. The data interleaver 2then reassembles new data packets incorporating small sections from manydifferent supplemental data packets. Each one of the reassembled packetsare 184 bytes long.

As described above, the purpose of the data interleaver 2 is to preventlosing of one or more packets due to noise or other harmful transmissionenvironment. By interleaving data into many different packets, even ifone packet is completely lost, the original packet may be recovered frominformation contained in other packets.

However, because there is a data interleaver in the ATSC 8T-VSBtransmission system, the data interleaver for the supplemental data canbe omitted if it is not required to enhance the burst noise performanceof the supplemental data. For this reason, the data interleaver 2 maynot be necessary for the VSB supplemental data encoder 8.

The VSB supplemental data encoder 8 also includes the null sequenceinserter 3 for inserting a null sequence to an allocated region of theinterleaved (if the data interleaver 2 was present) or Reed-Solomoncoded supplemental data for generating the predefined sequence for thesupplemental data at an input terminal of a Trellis coder (shown in FIG.1B). The null sequence is inserted so that the VSB reception systemreceives the supplemental data more reliably, even in a noisy channel ora multipath fading channel.

Further referring to FIG. 1A, the VSB supplemental data encoder 8includes the MPEG header inserter 4 for adding an MPEG header to thesupplemental data having the null sequence inserted thereto, forbackward-compatibility with the legacy VSB reception system. Because theMPEG-II data supplied to the VSB transmission system 6 is 187 byteslong, the MPEG header inserter 4 places, preferably, three headers infront of each packet (which was 184 bytes) to form a 187 byte longpacket identical to the MPEG-II data packet.

The supplemental data having the MPEG header added thereto is providedto a multiplexer 5. The multiplexer 5 receives as inputs the processedsupplemental data from the MPEG header inserter 4 and MPEG data packets.MPEG data packet, such as a broadcasting program (movie, sports,entertainment, or drama), coded through another path (preferably anoutput from an MPEG encoder), is received together with the supplementaldata at the multiplexer 5. Upon reception of the MPEG data and thesupplemental data, the multiplexer 5 multiplexes the supplemental dataand the MPEG data at a fixed ratio in a time division manner in segmentunits under the control of a controller defining a multiplexing ratioand unit and forwards the multiplexed data to the 8T-VSB transmissionsystem 6. According to the present invention, 313 data segments arecombined to make one data field.

The VSB transmission system 6, which is described in detail in referenceto FIG. 1B, processes the multiplexed data and transmits the processeddata to the VSB reception system through the antenna 7.

The operation of the 8T VSB transmission system 6 will be explained withreference to FIG. 1B. The packets multiplexed in segment units areprocessed at the VSB transmission system 6. There is a data randomizer11 in FIG. 1B for making the multiplexed packets random, and aReed-Solomon coder 12 for subjecting the randomized data to Reed-Solomoncoding and adding a parity code of 20 bytes to each of the randomizeddata packets. The data interleaver 13 interleaves the Reed-Solomon codedpackets. The Trellis coder 14 converts the bytes of the interleaved datapackets into symbols and subjecting them to Trellis coding.

As described above, the packets are interleaved to provide symbols fromone packet to be interleaved into many packets before being forwarded tothe Trellis coder 14. There is a multiplexer 15 for multiplexing asymbol stream and for synchronizing signals, and a pilot inserter 16 foradding pilot signals to the symbol streams. There is a VSB modulator 17for modulating the symbol stream into 8T-VSB signals. There is a RFconverter 18 for converting a base band signal, an 8T-VSB signal, into aRF band signal, which is transmitted to the reception system through anantenna 7.

Both a Trellis decoder and a slicer predictor in the digital VSBreception system shown in FIG. 11 use a Viterbi algorithm for estimationof sequence of state transition. An ACS (Accumulate/Compare/Select) partin the Viterbi algorithm calculates metrics of all the possible pathsfor all states, selects a path with the minimum value (the maximumlikelihood), and stores a corresponding metric value. In this instance,a path metric calculated presently is a path metric of a prior timecorresponding to the path added with a branch metric. Accordingly, thepath metrics calculated up to a prior symbol influence the followingsymbols.

While a predefined sequence is inserted in the symbols of thesupplemental data at the VSB transmission system, no predefined sequenceis included in the symbols of the MPEG data. This causes the reliabilityof an accumulated path metric to be reduced in a symbol section of theMPEG transport data than a symbol section of the supplemental data.Therefore, when the symbols of the MPEG data and the symbols of thesupplemental data are mixed, the symbols of the MPEG data giveinfluences to the symbols of the supplemental data. This situationcauses the decoding performance of the symbols of the supplemental datato be inferior.

Because the range of the influence is a few symbols, there is adifference (an error rate) of decoding performances between the symbolsof the supplemental data in the vicinity of the influence range and thesymbols of the supplemental data positioned somewhat away from theinfluence range. In other words, for the symbols corresponding to thesupplemental data, the error rate of the symbols of the supplementaldata is higher on a boundary between the symbol section of MPEGtransport data and the symbol section of the supplemental data.

Accordingly, in order to maximize the decoding performance of thesupplemental data symbols, it is preferable that the supplemental datasymbols are transmitted in succession or in large groups. It is requiredthat there is at least a boundary between the symbol section of the MPEGtransport data and the symbol section of the supplemental data. Theboundary is closely related to the multiplexer, the interleaver, and theTrellis coder.

FIG. 2 illustrates an example of multiplexing the supplemental data andthe MPEG data at a multiplexing ratio of 2:6. This is an example where adecoding performance of the supplemental data symbols is less thandesirable. The left side diagram illustrates a data field segmentdiagram in a case when multiplexing is made to include two supplementaldata segments and six MPEG segments to form a data field. The right sidediagram illustrates the same data field (as the left side diagram)having first 52 bytes and the next 52 bytes provided from the datainterleaver 13 to coders in the Trellis coder 14. Preferably, there are12 coders and precoders in the Trellis coder 14 as shown in FIG. 9. Eachcolumn in the right side diagram represents input to each coder in theTrellis coder 14. As can be perceived from the drawing, since themultiplex pattern is not in a 12 byte cycle, bytes of the supplementaldata are not grouped on a particular Trellis coder.

FIGS. 3 and 4 illustrate preferred examples of multiplexing. FIG. 3illustrates a diagram showing an example where the supplemental data andMPEG data are multiplexed in a 1:3 ratio. FIG. 4 illustrates a diagramshowing an example where supplemental data and MPEG data are multiplexedin a 1:1 ratio.

A basic principle of multiplexing the supplemental data and the MPEGdata according to the preferred embodiment of the present invention willbe explained. The principle of multiplexing of the present invention isbased on a number of supplemental data packets (denoted as P). When aperiod of the multiplex pattern for forming a data field is assumed tobe 4 segments, a decoding performance of the supplemental data ismaximized. One supplemental data packet corresponds to two segments, and0 to 156 (=312/2) supplemental data packets may be multiplexed in onedata field. The supplemental data multiplexed with the MPEG data in afour-segment period are bunched and provided to the Trellis coder 14through the data interleaver 13.

Using the above information, rules expressed in the following equationsmay be formulated. A map may be provided by using the followingequations for multiplexing the supplemental data segments in the VSBdata field. The supplemental data segments are multiplexed in the VSBdata field, according to the following equations. $\begin{matrix}{{{0 \leq P \leq 39}:{MAP}} = \left\{ {{{s❘s} = {\left( {\left( {{4i} + {K1}} \right)\quad{mod}\quad 312} \right) + 1}},{i = 0},1,\ldots\quad,{{2P} - 1}} \right\}} & (1) \\\begin{matrix}{{{40 \leq P \leq 78}:{MAP}} = {\left\{ {{{s❘s} = {\left( {\left( {{4i} + {K1}} \right)\quad{mod}\quad 312} \right) + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {\left( {\left( {{4i} + {K2}} \right)\quad{mod}\quad 312}\quad \right) + 1}},{i = 0},1,\ldots\quad,{{2P} - 79}} \right\}}\end{matrix} & (2) \\\begin{matrix}{{{79 \leq P \leq 117}:{MAP}} = {\left\{ {{{s❘s} = {\left( {\left( {{4i} + {K1}} \right)\quad{mod}\quad 312} \right) + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {\left( {\left( {{4i} + {K2}} \right)\quad{mod}\quad 312} \right) + 1}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {\left( {\left( {{4i} + {K3}} \right)\quad{mod}\quad 312} \right) + 1}},{i = 0},1,\ldots\quad,{{2P} - 157}} \right\}}\end{matrix} & (3) \\\begin{matrix}{{{118 \leq P \leq 156}:{MAP}} = {\left\{ {{{s❘s} = {\left( {\left( {{4i} + {K1}} \right)\quad{mod}\quad 312} \right) + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {\left( {\left( {{4i} + {K2}} \right)\quad{mod}\quad 312} \right) + 1}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {\left( {\left( {{4i} + {K3}} \right)\quad{mod}\quad 312} \right) + 1}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {\left( {\left( {{4i} + {K4}} \right)\quad{mod}\quad 312} \right) + 1}},{i = 0},1,\ldots\quad,{{2P} - 235}} \right\}}\end{matrix} & (4) \\{1 \leq s \leq 312} & (5) \\{{0 \leq {K1}},{K2},{K3},{{K4} \leq 311}} & (6) \\{\left( {{Km}\quad{mod}\quad 4} \right) \neq {\left( {{Kn}\quad{mod}\quad 4} \right)\quad{for}\quad m} \neq n} & (7) \\{{1 \leq m},{n \leq 4}} & (8)\end{matrix}$

In above equations (1) to (8), the ‘s’ indicates a segment position inthe data field offset from the field synchronizing signal location andhas a value ranging from 1 to 312. The K1, K2, K3, and K4 indicateoffsets for adjusting the starting positions for multiplexing thesupplemental data segments with reference to the field synchronizingsignal, and have a value ranging from 0 to 311. (Km mod 4) and (Kn mod4) have different values for different values of ‘m’ and ‘n’.

The above equations may be summarized such that, in a case where anumber of the supplemental data segments to be multiplexed in one datafield is smaller than ¼ of 312 segments (0≦P≦39), a position of thesupplemental data segment is assigned to every fourth segment of thedata field, starting from a particular position of the data field.

Where the number of the supplemental data segments to be multiplexed inone data field is greater than ¼ of 312 bytes but smaller than ½ of 312(40≦P≦78), a position of the supplemental data segment is assigned toevery fourth segment of the data field starting from a particularposition of the data field. Then, for rest of the supplemental datasegments, a position of the supplemental data segment is assigned toevery fourth segment of the data field starting from another particularposition of the data field.

Where the number of the supplemental data segments to be multiplexed inone data field is greater than ½ of 312 bytes but smaller than ¾ of312(79≦P≦117), a position of the supplemental data segment is assignedto every fourth segment of the data field starting from a particularposition of the data field for ½ of the positions of the supplementaldata segments to be multiplexed. Then, for the rest of the supplementaldata segments, a position of the supplemental data segment is assignedto every fourth segment of the data field starting from anotherparticular position of the data field, i.e., taking a different startingposition of multiplexing the supplemental data.

Where the number of the supplemental data segments to be multiplexed inone data field is greater than ¾ of 312 bytes but smaller than 1(118≦P≦156), a position of the supplemental data segment is assigned toevery fourth segment of the data field starting from a particularposition of the data field for ¾ of the positions of the supplementaldata segments to be multiplexed. Then, for the rest of the supplementaldata segments, a position of the supplemental data segment is assignedto every fourth segment of the data field starting from anotherparticular position of the data field, i.e., taking a different startingposition of multiplexing the supplemental data.

In equations (1) to (8), the offset values K1, K2, K3, and K4 are set tobe in a range of ‘0’ to 311, to generalize the starting position ofmultiplexing the supplemental data segments in the data field. If thefour offset values K1, K2, K3, and K4 are fixed and used in the VSBcommunication system, the values are not required to be included in themultiplexing information.

Examples of multiplexing the MPEG segments and the extra segmentsaccording to equations (1) to (8) will be explained with reference tothe drawings. FIG. 5A illustrates a diagram showing a multiplexed datafield when the supplemental data segments and the MPEG data segments aremultiplexed in a 1:3 ratio with the offset K1 set to ‘0’. FIG. 5Billustrates a diagram showing a multiplexed data field when thesupplemental data segments and the MPEG data segments are multiplexed ina 1:3 ratio with the offset K1 set to ‘1’. FIG. 5C illustrates a diagramshowing a multiplexed data field when the supplemental data segments andthe MPEG data segments are multiplexed in a 1:3 ratio with the offset K1set to ‘2’. FIG. 5D illustrates a diagram showing a multiplexed datafield when the supplemental data segments and the MPEG data segments aremultiplexed a 1:3 ratio with the offset K1 set to ‘3’. FIGS. 5A to 5Dcorrespond to an example where the number ‘P’ of supplemental datapackets are 39.

In each figure, a diagram on the left side illustrates a form ofmultiplexing the supplemental data segments and the MPEG data segmentswith reference to the field synchronizing signal. A diagram on the rightside illustrates a form of an output signal of the interleaver asprovided to twelve Trellis coders residing in the Trellis coder 14,respectively.

FIG. 5A illustrates data field and trellis coder input diagrams showingthe supplemental data segment being multiplexed for every fourth datafield segments starting from a first segment of the data field withreference to the field synchronizing signal. The diagram on the rightside illustrates the first 52 bytes of supplemental data and the second52 bytes of supplemental data from the interleaver being provided to 12Trellis coders next to the field synchronizing signal. That is, thefirst 52 bytes of supplemental data are provided to the 12 Trelliscoders by 12 bytes over four times (48 bytes), leaving four bytes amongthe 52 bytes. The four remaining bytes are provided to the 12 Trelliscoders together with the first 8 bytes of the second 52 bytes.

According to the multiplexing pattern of the supplemental data expressedin equations (1) to (8), the four remaining bytes among the first 52bytes maintain a fixed multiplexing pattern with the first 8 bytes amongthe second 52 bytes. This implies that bytes of the supplemental dataare grouped to a particular coder or coders among the twelve Trelliscoders. The multiplexing of the supplemental data with the bytes groupto a particular coder or coders enhances the decoding performance of thesupplemental data at the VSB reception system.

FIG. 5B illustrates data field and trellis coder input diagrams showingthe supplemental data segment being multiplexed starting from a secondsegment of the data field with reference to the field synchronizingsignal. FIG. 5C illustrates a diagram showing the supplemental datasegment being multiplexed starting from a third segment of the datafield with reference to the field synchronizing signal. FIG. 5Dillustrates a diagram showing the supplemental data segment beingmultiplexed starting from a fourth segment of the data field withreference to the field synchronizing signal. The cases of FIG. 5B to 5Dare identical to the case of FIG. 5A in that one supplemental datasegment is multiplexed for every four segments of the data field, andbytes of the supplemental data are grouped in a particular coder orcoders.

Cases where the supplemental data segments and the MPEG data segmentsare multiplexed in a ratio of 1:1 by using equations (1) to (8) will beexplained. FIG. 6A illustrates a diagram showing a multiplexed datafield when the supplemental data segments and the MPEG data segments (orMPEG transport segments) are multiplexed in a 1:1 ratio with the offsetK1 set to ‘0’ and the offset K2 set to 1. FIG. 6B illustrates a diagramshowing a multiplexed data field when the supplemental data segments andthe MPEG data segments (or MPEG transport segments) are multiplexed in a1:1 ratio with the offset K1 set to ‘0’ and the offset K2 set to 2.

Referring to FIGS. 6A and 6B, it can be seen that the followingsituation occurs in the multiplexed data field. FIGS. 5A to 5Dillustrate examples where the MPEG data segments (or the MPEG transportsegments) are multiplexed in a 1:3 ratio. In this instance, thesupplemental data bytes are grouped to a particular coder or coders evenif the starting positions of the supplemental data multiplexing differwith reference to the field synchronizing signal. Therefore, by acombination of any two cases of FIGS. 5A to 5D, a characteristicidentical to the case when the MPEG data segments (or the MPEG transportsegments) are multiplexed in a 1:3 ratio can be maintained even if theMPEG data segments (or the MPEG transport segments) are multiplexed in a1:1 ratio.

For an example, if the cases of FIGS. 5A and 5B are combined, thesupplemental data bytes are grouped to a particular Trellis coder asshown in FIG. 6A. If the cases of FIGS. 5A and 5C are combined, thesupplemental data bytes are bunched to a particular Trellis coder asshown in FIG. 6B.

Equations (9) to (12) are a summary of methods for multiplexing the MPEGdata segments (or MPEG transport segments) and the supplemental datasegments according to the number of the supplemental data packets whenthe offset values K1, K2, K3, and K4 in the equations (1) to (8) arefixed to 0, 2, 1, and 3 respectively. P denotes a number of supplementaldata packets to be multiplexed in one data field. MAP denotes a set oflocations the supplemental data are multiplexed in one data field.

Preferably, the P value is divided into four regions, and thesupplemental data and the MPEG transport data in each region aremultiplexed differently. In equations 9 to 12, an element ‘s’ in a setrepresents a segment position in a data field from the location of thefield synchronizing signal. Once ‘P’ is fixed, then the MAP isdetermined. Then the supplemental data segments are multiplexed with theMPEG transport data in an order of the ‘s’ in the MAP. $\begin{matrix}{{{{0 \leq P \leq 39}:{MAP}} = \left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,{{2P} - 1}} \right\}},\left( {1 \leq s \leq 312} \right)} & (9) \\\begin{matrix}{{{40 \leq P \leq 78}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,{{2P} - 79}} \right\},\left( {1 \leq s \leq 312} \right)}\end{matrix} & (10) \\\begin{matrix}{{{79 \leq P \leq 117}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 2}},{i = 0},1,\ldots\quad,{{2P} - 157}} \right\},\left( {1 \leq s \leq 312} \right)}\end{matrix} & (11) \\\begin{matrix}{{{118 \leq P \leq 156}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 2}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 4}},{i = 0},1,\ldots\quad,{{2P} - 235}} \right\},\left( {1 \leq s \leq 312} \right)}\end{matrix} & (12)\end{matrix}$

As explained above, FIG. 3 illustrates a case when the supplemental dataand the MPEG data are multiplexed at a 1:3 ratio, where equation (9) isapplicable corresponding to a case where ‘P’ falls in the range 0≦P≦39.FIG. 4 illustrates a case when the supplemental data and the MPEG dataare multiplexed at a 1:1 ratio, where equation (10) is applicable in thecase where ‘P’ falls between 40≦P≦78. The data multiplexed according tothe foregoing methods is processed through the data interleaver 13 andthe Trellis coder 14 in the 8T VSB transmission system 6.

FIG. 7 illustrates a diagram showing a data interleaver. FIG. 8illustrates a diagram showing data input/output orders of the datainterleaver in FIG. 7. FIG. 9 illustrates a functional diagram of aTrellis coder, when the 8T VSB transmission system transmits themultiplexed data in succession for making the supplemental data decodingperformance to be at a maximum level. The process for multiplexing thesupplemental data and the MPEG data in 1:3 will be explained in detail,with reference to FIGS. 7 to 9.

As stated above, FIG. 7 illustrates the data interleaver in the VSBtransmission system, where a convolutional interleaver has B brancheswhere B is preferably 52 and M bytes of unit memories, where M ispreferably 4. As shown in FIG. 7, the interleaver is operativesynchronous to a first byte of one data field. The first byte isreceived and directly forwarded through the first branch, and a secondbyte is received through the second branch and a value 52×4 bytes priorto the second byte is forwarded.

FIG. 8 illustrates a diagram showing input/output orders of the datainterleaver in FIG. 7. In FIG. 8, the data is received from an upperside to a lower side of the data field in segment units, and bytes ineach segment are received from left to right. Numerals in FIG. 8represent the forwarding order of the interleaver shown in FIG. 7. Thefirst byte of the data field next to a field synchronizing signal isreceived at the first branch in FIG. 7 and forwarded directly as is. Thefirst byte corresponds to a numeral ‘1’ in FIG. 8. The next byte isreceived at the second branch of the interleaver.

As shown in FIG. 7, the interleaver forwards a byte received 52×4(M)=208 bytes prior to the next byte, to forward a byte corresponding toa numeral 2 as shown in FIG. 8. Upon reception of the next byte, theinterleaver forwards a byte 52×8 (2M)=416 bytes prior to the receivedbyte, to forward a byte corresponding to a numeral 3 as shown in FIG. 8.According to the foregoing method, 52 bytes from the interleaver areforwarded to the 12 Trellis coders and pre-coders (shown in FIG. 9) insuccession. A 53rd byte is received at the first branch of theinterleaver and directly forwarded. The interleaver is operative in a 52segment depth, and connected to the 12 Trellis coders and precoders.Therefore, the 52 bytes from the interleaver are forwarded to theTrellis coders and the precoders by 12 bytes in a cycle period of fourtimes.

In this instance, when the process is carried out for four times, only48 bytes (12 bytes×4 times=48) are forwarded to the Trellis coders andthe precoders, leaving 4 bytes. The remaining 4 bytes are forwarded tothe 12 Trellis coders and the precoders together with first 8 bytes ofthe next 52 bytes. Therefore, multiplexing the supplemental data andMPEG transport data segments with a period of 4 maximizes bunching thesupplemental data symbols into Trellis coders.

FIG. 9 illustrates a functional diagram of a Trellis coder 14 used inthe VSB transmission system 6 of the present invention. The inputs andoutputs to the twelve (12) Trellis coders and the precoders aremultiplexed. As shown in FIG. 9, the 12 bytes form the interleaverprovided to the 12 Trellis coders and the precoders by one byte, wheneach of the bytes are subjected to Trellis coding, to produce 4 symbols(each symbol has two bits). The symbols from each of the Trellis codersare multiplexed by one symbol before the symbols are forwarded.

FIG. 10 illustrates a segment structure of a field synchronizing signalsegment in a data field of the VSB transmission system of the presentinvention. In FIG. 10, the segment of the field synchronizing signalcontains the multiplexing information to be used by the VSB receptionsystem. The VSB reception system detects the multiplexing information inthe segment containing the field synchronizing signal and performs thecorrect decoding by using the multiplexed information.

As explained, once the number ‘P’ (0 to 156) of the supplemental datapackets is fixed, the multiplexed positions of the supplemental data arefixed in the data field. The VSB transmission system then transmits onlya ‘P’ value to the VSB reception system.

For facilitating a quantity change of the supplemental data to bemultiplexed even if it is in the middle of transmission of data from theVSB transmission system to the VSB reception system, the VSBtransmission system transmits the current ‘P’ value, a number of datafields until the present ‘P’ value is changed (i.e, a count down valueuntil the P value change occurs), and a ‘P’ value to be changed in thereserved area of the field synchronizing signal segment shown in FIG. 10to the VSB reception system.

Accordingly, the VSB reception system receives data without any errorfrom the VSB transmission system, even if the ‘P’ value is changed. Themultiplexing information is contained in the reserved area of the fieldsynchronizing signal.

As shown in FIG. 10, of the total 832 symbols of the field synchronizingsignal segment, 92 symbols are assigned to the reserved area. Forexample, the multiplexing information transmitted through the reservedarea is as follows. 8 bits may be assigned to the current ‘P’ value,another 8 bits are assigned to the ‘P’ value to be changed, and another8 bits are assigned to a number of fields until the current ‘P’ value ischanged to a next ‘P’ value. Therefore, a total of 24 bits of themultiplexing information is transmitted to the VSB reception systemusing the reserved area. If the count down value until change is ‘0’, itimplies that the current ‘P’ value will not be changed for the timebeing. At this time, the next P value is the same with the current Pvalue.

Even in a case when comb filtering is carried out in the VSB receptionsystem due to the interference from an NTSC broadcasting signal, thepresent broadcasting type, detection of the multiplexing information isrequired. To accommodate for such situation, the entire 24 bits ofmultiplexing information is preferably divided into two 12 bit pieces ofinformation, where one of the two pieces of 12 bit information has aform inverted with respect to the other. That is, one piece of 12 bitinformation is transmitted to the VSB reception system, together withanother piece of 12 bit information inverted to the first piece of 12bit information.

As shown in FIG. 10, the 24-bit multiplexing information is divided intotwo 12-bit sections of information. The first 12-bit section and thesecond 12-bit section are inverse of each other and occupy the reservedarea. Preferably, the inversion is a bit-wise-inversion.

For more stable transmission of the multiplexing information from theVSB transmission system to the VSB reception system under a poor channelsituation (in a form that the multiplexing information is included to afirst supplemental data segment next to the field synchronizing signal),the multiplexing information may be transmitted to the VSB receptionsystem as part of the supplemental data segment.

FIG. 11 illustrates a block diagram of a digital VSB reception system300 in accordance with a preferred embodiment of the present invention,which improves reception performance by using a predefined sequence andreceives supplemental data transmitted by the VSB transmitter.

In FIG. 11, the VSB reception system 300 of the present inventionincludes a sequence generator 31 for indicating a symbol of thesupplemental data and generating a predefined sequence included in thesupplemental data, a modified legacy VSB receiver 32 for processing thedata received from the VSB transmitter 110 (shown in FIG. 1A) in areverse order of the VSB transmission system. The VSB reception system300 further includes a demultiplexer 34 for demultiplexing the data fromthe modified legacy VSB receiver 32 into the MPEG data (also known asdata segment) and the supplemental data (also known as data segment),and a supplemental data decoder 35 for processing the supplemental datasegment from the demultiplexer 34 in reverse order of the transmissionsystem, to obtain the original supplemental data.

As shown in FIG. 11, the modified legacy VSB receiver 32 includes ademodulator 41, a comb filter 42, a channel equalizer 43, a slicerpredictor 44, a phase tracker 45, a Trellis decoder 46, a first datadeinterleaver 47, a first Reed-Solomon decoder 48, and a datade-randomizer 49. The supplemental data decoder 35 includes an MPEGheader remover 51, a null sequence remover 52, a second datadeinterleaver 53, and a second Reed-Solomon decoder 54.

According to the preferred embodiment, the demodulator 41 converts a RFband signal into a base band signal, and the synchronizing and timingrecovery system recovers a segment synchronizing signal, a fieldsynchronizing signal, and a symbol timing. The comb filter 42 removes anNTSC interference signal, if detected, and the channel equalizer 43corrects a distorted channel by using the slicer predictor 44.

The phase tracker 45 corrects a rotated phase, and the Trellis decoder46 undertakes Viterbi decoding by using the generated sequence and theViterbi algorithm. The channel equalizer 43, the slicer predictor 44,the phase tracker 45, and the Trellis decoder 46 process the receivedsymbols by using the sequence generated at the sequence generator 31.

The first data deinterleaver 47 acts in reverse of the action of thedata interleaver in the ATSC 8T VSB transmission system. The firstReed-Solomon decoder 48 again decodes a signal Reed-Solomon coded at theATSC 8T VSB transmission system. The data derandomizer 49 acts inreverse of the action of the data randomizer in the transmission system.

According to the preferred embodiment of the present invention thesequence generator 31 decodes the symbol received from the VSBtransmission system corresponding to the supplemental data, andgenerates a sequence identical to the predefined sequence that isinserted and transmitted in the supplemental data.

As described above, the channel equalizer 43, the slicer predictor 44,the phase tracker 45, and the Trellis decoder 46 improve signalprocessing performances by using the predefined sequence. This occurswhen the components using the predefined sequence use the sequenceinformation with the delayed sequence information, taking the delay indata processing at prior components into account.

In the VSB reception system 300, the demultiplexer 34 demultiplexes thedata from the modified legacy VSB receiver 32 into a supplemental datasegment and an MPEG data segment by using the multiplexing informationdetected from, for example, the field synchronizing signal. In thepreferred embodiment the first Reed-Solomon decoder 54 makes noReed-Solomon decoding of the supplemental data segment, but only removesthe 20 byte parity added at the Reed-Solomon coder in the VSBtransmission system.

If the channel noise is excessive, many errors are present in the paritybytes of the Reed-Solomon code compared to the supplemental data becausethe parity bytes of the ATSC Reed-Solomon code has no predefinedsequence inserted, resulting in no gain at the Trellis decoder 46. Thefirst Reed-Solomon decoder 48 makes no Reed-Solomon decoding of thesupplemental data segment because it is highly possible that the firstReed-Solomon decoder 48 makes an erroneous correction in the case wherethe supplemental data segment has an error in excess of, for example, 10bytes.

The supplemental data segment from the demultiplexer 34 is provided tothe MPEG header remover 51. The MPEG header remover 51 removes 3 bytesof MPEG header from the supplemental data segment. The MPEG header isinserted when the supplemental data is transmitted in an ATSC format atthe VSB transmission system.

The null sequence remover 52 then removes the null sequence inserted inthe supplemental data segment at the null sequence inserter in the VSBtransmission system. The second data deinterleaver 53 acts in reverse ofthe interleaving process on the supplemental data segment in the VSBtransmission system. If the interleaving process is omitted in the VSBtransmission system, the VSB reception system 300 may disable the seconddeinterleaver 53 or not include it at all. The second Reed-Solomondecoder 54 decodes the Reed-Solomon code of the supplemental datasegment.

Since the predefined sequence is inserted in the supplemental datasymbol only, the VSB reception system 300 is required to identify thesupplemental data symbol, and to determine whether the predefinedsequence from the transmission system is ‘0’ or ‘1’.

The VSB reception system 300 in FIG. 11 improves a reception performanceby using the predefined sequence inserted at the VSB transmissionsystem. Referring to FIG. 11, the multiplexing information detector 33detects the multiplexing information contained in the reserved area ofthe field synchronization signal segment and outputs a demultiplexingcontrol signal. The demultiplexer 34 received the demultiplexing controlsignal for separating the bitstream into the supplemental data and theMPEG data packets by using the multiplexing information.

If the multiplexing information is included at the first supplementaldata segment next to the field synchronization signal, then themultiplexing information detector 33 extracts that information from thedecoded supplemental data and uses this for more robust tracking ofmultiplexing information. Also, when the received data is thesupplemental data, the multiplexing information detector 33 provides ademultiplexing control signal which facilitates bypassing of the firstReed-Solomon decoder 48 and thus not making the first Reed-Solomondecoding by using the multiplexing information from the fieldsynchronizing signal.

FIG. 12 illustrates a block diagram of the multiplexing informationdetector 33 according to the preferred embodiment of the presentinvention. According to FIG. 12, the multiplexing information detector33 includes a 2-level slicer 202, a serial-to-parallel converter 204, amultiplexing information extractor 206, and ancillary devices, such asflip-flop 208, comparator 210, confidence counter 214 and error detector212.

The 2-level slicer 202 decides the sign of the received data from, forexample, the phase tracker 45 of the modified legacy VSB receiver 32.The serial-to-parallel converter 204 converts the bit stream of themultiplexing information to 48-bit parallel data. The multiplexinginformation extractor 206 extract only the 24-bit multiplexinginformation (also referred to as payload data b23 . . . b0) out of the48-bit data discarding the comb filter compensation bits. The 24-bitflip-flop latches the multiplexing information to the sequence generator31, the first Reed-Solomon decoder 48 and the demultiplexer 34. Theerror detector 212 checks if the compensation bits [{overscore (b23 . .. b0)}] are the complements (e.g., negated [b23 . . . b0]) of payloadbits [b23 . . . b0] and if [b23 . . . b16] equals [b7 . . . b0] when[b15 . . . b8]=0×00. If error is detected, the error detector holds theconfidence counter 214.

Referring to FIG. 12, the comparator 210 compares the multiplexinginformation of current field segment with the ones of previous field(the content of the flip-flop 208). If they are the same, then thecomparator 210 causes the confidence counter 214 to be incremented byone. If not the same, then the confidence counter 214 is decreased byone. The confidence counter 214 sets the lock signal to “1” if thecounter value is greater than a threshold. If the lock signal isenabled, a transition from an acquisition process to a tracking processoccurs.

In FIG. 12, the enable signals provided to the various components of themultiplexing information detector 33 allows such components to bepreferably enabled near the end of each field sync segment.

The above described process allows the VSB receiver to reliably andsimply acquire the multiplexing information by correlation. This processis called an acquisition process. It is also necessary, for the VSBreceiver, which has already acquired the information by correlation offield sync data, to be then able to instantly and reliably track changesin the P value (number of supplemental data packets in a field).

In this regard, the multiplexing information from a data field,excluding the comb filter compensation bits, is duplicated in the firstsupplemental segment of the data field. As a result, the VSB receivertracks changes more reliably using robustly coded multiplexinginformation contained in the first supplemental segment. If the VSBreceiver finds that the multiplexing information previously acquired byfield sync correlation does not match the one in the first supplementalsegment, the multiplexing information detector restart the acquisitionprocess.

The VSB communication system of the present invention has the followingadvantages. First, the use of the predefined sequence and themultiplexing information in transmission of the MPEG data and thesupplemental data on a channel makes the VSB communication system of thepresent invention more robust to channel impairment.

Second, the VSB communication system of the present invention hasbackward compatibility with the related art VSB reception system.

Third, the use of the predefined sequence and the multiplexinginformation permits the VSB communication system of the presentinvention to receive the supplemental data without an error even on achannel having ghost and noise heavier than the related art VSBcommunication system.

Fourth, the multiplexing of the supplemental data and the MPEG dataunder a fixed rule improves the decoding performance of the supplementaldata in the VSB reception system.

Fifth, the broadcaster can change the number of supplemental packets tobe multiplexed (i.e., the P value).

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the VSB communication systemof the present invention without departing from the spirit or scope ofthe invention. Thus, it is intended that the present invention cover themodifications and variations of this invention provided they come withinthe scope of the appended claims and their equivalents.

1-48. (canceled)
 49. A VSB field synchronizing signal segment for use ina VSB transmitter with a supplemental data coder and a VSB receiver witha supplemental data decoder, the VSB transmitter transmitting at leastone data field containing a plurality of main and supplemental datasegments, the field synchronizing signal segment comprising: a segmentsynchronizing symbol area; at least one training symbol area; a VSB modesymbol area; a precode symbol area; and a reserved area includingmultiplexing information indicating a number of the supplemental datasegments in the data field.
 50. The VSB field synchronizing signalsegment of claim 49, wherein positions of the supplemental data segmentsin the data field are based on the number of the supplemental datasegments.
 51. The VSB field synchronizing signal segment of claim 49,wherein the segment synchronizing symbol area contains 4 symbols, afirst training symbol area contains 511 symbols, a second trainingsymbol area contains 62 symbols, a third training symbol area contains63 symbols, the VSB mode symbol area contains 24 symbols, the precodesymbol area contains 12 symbols, and the reserved area contains 92symbols.
 52. An enhanced VSB transmitter for transmitting main data andsupplemental data, the enhanced VSB transmitter comprising: a VSBpre-processor for coding original supplemental data packets for firstforward error correction (FEC) and enhancing the first FEC coded datapackets by inserting a plurality of null bits into each packet; a firstmultiplexer for multiplexing the enhanced supplemental data packets withmain data packets in a data field based on a number of the originalsupplemental data packets, the data field containing a plurality of mainand supplemental data segments and a field synchronizing signal segment,the field synchronizing signal segment comprising a reserved areaincluding multiplexing information which indicates the number of theoriginal supplemental data packets; a VSB main processor for coding themultiplexed data packets for second forward error correction (FEC); anda data format converter for formatting the second FEC coded data packetsfor transmission and transmitting the formatted data packets to one ormore VSB receivers.
 53. The enhanced VSB transmitter of claim 52,wherein the field synchronizing signal segment further comprises: asegment synchronizing symbol area; at least one training area; a VSBmode symbol area; and a precode symbol area.
 54. The enhanced VSBtransmitter of claim 52, wherein the positions of the supplemental datasegments in the data field are expressed by the following equations:$\begin{matrix}{{{{{{for}\quad 0} \leq P \leq 39}:{MAP}} = \left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,{{2P} - 1}} \right\}};} \\{{{{{for}\quad 40} \leq P \leq 78}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,{{2P} - 79}} \right\};} \\{{{{{for}\quad 79} \leq P \leq 117}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 2}},{i = 0},1,\ldots\quad,{{2P} - 157}} \right\};{and}} \\{{{{{for}\quad 118} \leq P \leq 156}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 2}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 4}},{i = 0},1,\ldots\quad,{{2P} - 235}} \right\};}\end{matrix}$ wherein “P” denotes a number of the original supplementaldata packets, and “s” denotes a supplemental data segment position withrespect to the field synchronizing signal segment within the data field.55. A method of transmitting main data and supplemental data, the methodcomprising: coding original supplemental data packets for first forwarderror correction (FEC); enhancing the first FEC coded supplemental datapackets by inserting a plurality of null bits into each coded packet;multiplexing the enhanced supplemental data packets and main datapackets in a data field based on a number of the original supplementaldata packets, the data field comprising a plurality of main andsupplemental data segments and a field synchronizing signal segment, thefield synchronizing signal segment comprising a reserved area includingmultiplexing information indicating the number of the originalsupplemental data packets; coding the multiplexed data packets forsecond forward error correction (FEC); formatting the second FEC codedmultiplexed data packets for transmission; and transmitting theformatted data packets to one or more VSB receivers.
 56. The method ofclaim 55, wherein the field synchronizing signal segment furthercomprises: a segment synchronizing symbol area; at least one trainingarea; a VSB mode symbol area; and a precode symbol area.
 57. The methodof claim 55, wherein the positions of the supplemental data segments inthe data field is are expressed by the following equations:$\begin{matrix}{{{{{{for}\quad 0} \leq P \leq 39}:{MAP}} = \left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,{{2P} - 1}} \right\}};} \\{{{{{for}\quad 40} \leq P \leq 78}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,{{2P} - 79}} \right\};} \\{{{{{for}\quad 79} \leq P \leq 117}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 2}},{i = 0},1,\ldots\quad,{{2P} - 157}} \right\};{and}} \\{{{{{for}\quad 118} \leq P \leq 156}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 2}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 4}},{i = 0},1,\ldots\quad,{{2P} - 235}} \right\};}\end{matrix}$ wherein “P” denotes a number of the original supplementaldata packets, and “s” denotes a supplemental data segment position withrespect to the field synchronizing signal segment within the data field.58. An enhanced VSB receiver for receiving main data and supplementaldata from a VSB transmitter, the enhanced VSB receiver comprising: amain VSB processor for receiving and decoding a data field comprising aplurality of multiplexed main and enhanced supplemental data segmentsand a field synchronizing signal segment, the field synchronizing signalsegment comprising a reserved area which includes multiplexinginformation indicating a number of original supplemental data packetsincluded in the data field; a multiplexing information detector fordetecting the multiplexing information from the field synchronizingsignal segment; a demultiplexer for demultiplexing the main datasegments and the enhanced supplemental data segments from the data fieldusing the detected multiplexing information; and a supplemental VSBprocessor for processing decoding the demultiplexed enhancedsupplemental data segments to obtain the original supplemental datapackets.
 59. The enhanced VSB receiver of claim 58, wherein the fieldsynchronizing signal segment further comprises: a segment synchronizingsymbol area; at least one training area; a VSB mode symbol area; and aprecode symbol area.
 60. The enhanced VSB receiver of claim 58, whereinthe positions of the enhanced supplemental data segments included in thedata field are expressed by the following equations: $\begin{matrix}{{{{{{for}\quad 0} \leq P \leq 39}:{MAP}} = \left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,{{2P} - 1}} \right\}};} \\{{{{{for}\quad 40} \leq P \leq 78}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,{{2P} - 79}} \right\};} \\{{{{{for}\quad 79} \leq P \leq 117}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 2}},{i = 0},1,\ldots\quad,{{2P} - 157}} \right\};{and}} \\{{{{{for}\quad 118} \leq P \leq 156}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 2}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 4}},{i = 0},1,\ldots\quad,{{2P} - 235}} \right\};}\end{matrix}$ wherein “P” denotes the number of the originalsupplemental data packets, and “s” denotes a supplemental data segmentposition with respect to the field synchronizing signal segment withinthe data field.
 61. A method of receiving main data and supplementaldata from a VSB transmitter, the method comprising: receiving anddecoding a data field comprising a plurality of multiplexed main andenhanced supplemental data segments and a field synchronizing signalsegment, the field synchronizing signal segment comprising a reservedarea which includes multiplexing information indicating a number oforiginal supplemental data packets included in the data field; detectingthe multiplexing information from the field synchronizing signalsegment; demultiplexing main data packets and enhanced supplemental datapackets from the data field using the detected multiplexing information;and coding the enhanced data packets to obtain the original supplementaldata packets.
 62. The method of claim 61, wherein the fieldsynchronizing signal segment further comprises: a segment synchronizingsymbol area; at least one training area; a VSB mode symbol area; and aprecode symbol area.
 63. The method of claim 61, wherein a MAP thepositions of the supplemental data segments included in the data fieldis are expressed by the following equations: $\begin{matrix}{{{{{{for}\quad 0} \leq P \leq 39}:{MAP}} = \left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,{{2P} - 1}} \right\}};} \\{{{{{for}\quad 40} \leq P \leq 78}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,{{2P} - 79}} \right\};} \\{{{{{for}\quad 79} \leq P \leq 117}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 2}},{i = 0},1,\ldots\quad,{{2P} - 157}} \right\};{and}} \\{{{{{for}\quad 118} \leq P \leq 156}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 2}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 4}},{i = 0},1,\ldots\quad,{{2P} - 235}} \right\};}\end{matrix}$ wherein “P” denotes the number of the originalsupplemental data packets, and “s” denotes a supplemental data segmentposition with respect to the field synchronizing signal segment withinthe data field.
 64. A VSB field synchronizing signal segment for use ina VSB transmitter with a supplemental data coder and a VSB receiver witha supplemental data decoder, the VSB transmitter transmitting at leastone data field containing a plurality of main and supplemental datasegments, the field synchronizing signal segment comprising: a firstarea for storing first information representing a number of thesupplemental data segments included in a current data field; and asecond area for storing second information to be used for determining acount down value indicating a next data field having a different numberof supplemental data segments.
 65. The VSB field synchronizing signalsegment of claim 64, wherein the first information occupies at least 8bits, and the second information occupies at least 8 bits.
 66. The VSBfield synchronizing signal segment of claim 64, further comprising: athird area for storing the different number of the supplemental datapackets included in the next data field.
 67. An enhanced VSB transmitterfor transmitting main data and supplemental data, the enhanced VSBtransmitter comprising: a VSB pre-processor for coding originalsupplemental data packets for first forward error correction (FEC) andenhancing the first FEC coded data packets by inserting a plurality ofnull bits into each data packet; a multiplexer for multiplexing theenhanced supplemental data packets and main data packets in a data fieldbased on a number of the original supplemental data packets, the datafield containing a plurality of main and supplemental data segments anda field synchronizing signal segment, the field synchronizing signalsegment comprising: a first area for storing first informationrepresenting the number of the original supplemental data packets; and asecond area for storing second information to be used for determining acount down value indicating a next data field having a different numberof original supplemental data packets; a VSB main processor for codingthe multiplexed data packets for second forward error correction (FEC);and a data format converter for formatting the second FEC coded datapackets for transmission and transmitting the formatted data packets toone or more VSB receivers.
 68. The enhanced VSB transmitter of claim 67,wherein the field synchronizing signal segment further comprises: athird area for storing the different number of the original supplementaldata packets included in the next data field.
 69. The enhanced VSBtransmitter of claim 67, wherein the positions of the supplemental datasegments in the data field are expressed by the following equations:$\begin{matrix}{{{{{{for}\quad 0} \leq P \leq 39}:{MAP}} = \left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,{{2P} - 1}} \right\}};} \\{{{{{for}\quad 40} \leq P \leq 78}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,{{2P} - 79}} \right\};} \\{{{{{for}\quad 79} \leq P \leq 117}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 2}},{i = 0},1,\ldots\quad,{{2P} - 157}} \right\};{and}} \\{{{{{for}\quad 118} \leq P \leq 156}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 2}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 4}},{i = 0},1,\ldots\quad,{{2P} - 235}} \right\};}\end{matrix}$ wherein “P” denotes a number of the original supplementaldata packets, and “s” denotes a supplemental data segment position withrespect to the field synchronizing signal segment within the data field.70. A method of transmitting main data and supplemental data, the methodcomprising: coding original supplemental data packets for first forwarderror correction (FEC) and enhancing the first FEC coded data packets byinserting a plurality of null bits into each packet; multiplexing theenhanced supplemental data packets and main data packets in a data fieldbased on a number of the original supplemental data packets, the datafield containing a plurality of main and supplemental data segments anda field synchronizing signal segment, the field synchronizing signalsegment comprising: a first area for storing first informationrepresenting the number of the original supplemental data packets; and asecond area for storing second information to be used for determining acount down value indicating a next data field having a different numberof original supplemental data packets; coding the multiplexed datapackets for second forward error correction (FEC); and formatting thesecond FEC coded data packets for transmission and transmitting theformatted data packets to one or more VSB receivers.
 71. The method ofclaim 70, wherein the field synchronizing signal segment furthercomprises: a third area for storing the different number of the originalsupplemental data packets included in the next data field.
 72. Themethod of claim 70, wherein the positions of the supplemental datasegments in the data field are expressed by the following equations:$\begin{matrix}{{{{{{for}\quad 0} \leq P \leq 39}:{MAP}} = \left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,{{2P} - 1}} \right\}};} \\{{{{{for}\quad 40} \leq P \leq 78}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,{{2P} - 79}} \right\};} \\{{{{{for}\quad 79} \leq P \leq 117}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 2}},{i = 0},1,\ldots\quad,{{2P} - 157}} \right\};{and}} \\{{{{{for}\quad 118} \leq P \leq 156}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 2}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 4}},{i = 0},1,\ldots\quad,{{2P} - 235}} \right\};}\end{matrix}$ wherein “P” denotes a number of the original supplementaldata packets, and “s” denotes a supplemental data segment position withrespect to the field synchronizing signal segment within the data field.73. An enhanced VSB receiver for receiving main and supplemental datafrom a VSB transmitter, the enhanced VSB receiver comprising: a main VSBprocessor for receiving and decoding a data field comprising a pluralityof multiplexed main and enhanced supplemental data segments and a fieldsynchronizing signal segment, the field synchronizing signal segmentcomprising: a first area for storing first information representing anumber of original supplemental data packets included in the data field;and a second area for storing second information to be used fordetermining a count down value indicating a next data field having adifferent number of original supplemental data packets; a multiplexinginformation detector for detecting the first and second information fromthe field synchronizing signal segment; a demultiplexer fordemultiplexing the main data segments and the enhanced supplemental datasegments from the data field using the detected first and secondinformation; and a supplemental VSB processor for processing decodingthe demultiplexed enhanced data segments to obtain the original datapackets.
 74. The enhanced VSB receiver of claim 73, wherein the fieldsynchronizing signal segment further comprises: a third area for storingthe different number of the original supplemental data packets includedin the next data field.
 75. The enhanced VSB receiver of claim 73,wherein the positions of the supplemental data segments in the datafield are expressed by the following equations: $\begin{matrix}{{{{{{for}\quad 0} \leq P \leq 39}:{MAP}} = \left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,{{2P} - 1}} \right\}};} \\{{{{{for}\quad 40} \leq P \leq 78}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,{{2P} - 79}} \right\};} \\{{{{{for}\quad 79} \leq P \leq 117}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 2}},{i = 0},1,\ldots\quad,{{2P} - 157}} \right\};{and}} \\{{{{{for}\quad 118} \leq P \leq 156}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 2}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 4}},{i = 0},1,\ldots\quad,{{2P} - 235}} \right\};}\end{matrix}$ wherein “P” denotes a number of the original supplementaldata packets, and “s” denotes a supplemental data segment position withrespect to the field synchronizing signal segment within the data field.76. A method of receiving main and supplemental data from a VSBtransmitter, the method comprising: receiving and decoding a data fieldcomprising a plurality of multiplexed main and enhanced supplementaldata segments and a field synchronizing signal segment, the fieldsynchronizing signal segment comprising: a first area for storing firstinformation representing a number of original supplemental data packetsincluded in the data field; and a second area for storing secondinformation to be used for determining a count down value indicating anext data field having a different number of original supplemental datapackets; detecting the first and second information from the fieldsynchronizing signal segment; demultiplexing the main data segments andthe enhanced supplemental data segments from the data field using thedetected first and second information; and processing the demultiplexedenhanced data segments to obtain the original data packets.
 77. Themethod of claim 76, wherein the field synchronizing signal segmentfurther comprises: a third area for storing the different number of theoriginal supplemental data packets included in the next data field. 78.The method of claim 76, wherein the positions of the supplemental datasegments in the data field are expressed by the following equations:$\begin{matrix}{{{{{{for}\quad 0} \leq P \leq 39}:{MAP}} = \left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,{{2P} - 1}} \right\}};} \\{{{{{for}\quad 40} \leq P \leq 78}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,{{2P} - 79}} \right\};} \\{{{{{for}\quad 79} \leq P \leq 117}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 2}},{i = 0},1,\ldots\quad,{{2P} - 157}} \right\};{and}} \\{{{{{for}\quad 118} \leq P \leq 156}:{MAP}} = {\left\{ {{{s❘s} = {{4i} + 1}},{i = 0},1,\ldots\quad,77} \right\} U}} \\{\left\{ {{{s❘s} = {{4i} + 3}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 2}},{i = 0},1,\ldots\quad,77} \right\} U} \\{\left\{ {{{s❘s} = {{4i} + 4}},{i = 0},1,\ldots\quad,{{2P} - 235}} \right\};}\end{matrix}$ wherein “P” denotes a number of the original supplementaldata packets, and “s” denotes a supplemental data segment position withrespect to the field synchronizing signal segment within the data field.